A YOUNG CUCKOO 81 



In making the above analyses, I have stated the 

 case for assimilation more liberally than strict 

 impartiality would have warranted. I have taken 

 no account of differences in size between Cuckoos' 

 eggs and those with which they were placed, although 

 such differences in about half of the examples are 

 monstrous, and many of these small eggs tell statis- 

 tically more than usually in favour of the theory of 

 assimilation. 



Whether the uniform assignment of 5 as the maxi- 

 mum for each of the criteria used in these analyses 

 represents their effective value upon the respective 

 foster-species, is fortunately of little consequence ; 

 for, the average results for these characteristics 

 are so nearly uniform that, in assigning a higher 

 value to one, it would be counterbalanced by the 

 lower value assigned to another, the general result 

 not being seriously affected. 



Upon the assumption that both of the eggs 

 present in Example 43 are Cuckoos' eggs, they 

 emphasize the fact, otherwise generally observable, 

 that Cuckoos' eggs differing in shape, size, colour, 

 and markings, are laid in nests of the same species. 

 If the first egg be not a Cuckoo's (I incline to accept 

 it as such) it serves to show that the eggs of the foster- 

 species themselves may vary in a way that would 

 lead them to be accepted as Cuckoos' eggs very 

 closely resembling the remainder of the clutch. 



The Cuckoo's egg of example 60 lies in glaring 

 contrast to three pure albinos of the Twite in the 

 same nest. Whether this argues lack of discrimina- 

 tion in the Cuckoo, the Twite, or both, makes equally 

 against the case for assimilation. 



